The goal of this program is to provide pre-doctoral students with strong research training in specific basic science disciplines in combination with broad training in parasitology. Faculty members of this T32 have diverse basic science interests and study at least 11 different parasitic infections and most have a strong record of sustained NIH funding. There are several major research themes within this faculty that include immunity to parasitic infection as well as the area of cell, molecular, and developmental biology of parasites. These interests are the underlying core of our program. As a group, we also offer didactic training in parasitology and provide an environment in which students will gain an appreciation for broader aspects of parasitic disease research. The program at Penn has seen considerable growth in the last 10 years with the doubling in the numbers of active trainers from 6 to 15 and the increased pool of eligible students (>30). This proposal requests 6 slots for a period of five years to support graduate students performing their thesis studies. Relevance to Public Health: The numbers of individuals affected by parasitic diseases are difficult to gauge but even the most conservative estimates of the global impact of diseases caused by parasites are extraordinary. For example, almost half of the world's population live in malaria-endemic areas and every year 1 to 2 million people die of this disease. Two billion people on Earth are infected by soil-transmitted helminths and early childhood infections by these worms contribute significantly to slowing of physical and cognitive development. While the study of parasites is closely linked to many aspects of tropical medicine, this group of organisms also poses a serious public health problem in the developed world.